The main function of a wound pad is to remove excessive exudate from a wound bed and prevent the removed exudate from returning to the wound bed if the wound pad is subjected to gravity forces or other external forces. A wound pad shall thus have good liquid acquisition properties (i.e. it should be easy for exudate to enter the wound pad), good liquid retention or holding properties (i.e. ability to prevent the exudate sucked up by wound pad to be pressed back to the wound bed by gravitational or other external forces). Furthermore, the absorption capacity, i.e. the amount of exudate that can be stored in the pad in a relaxed state thereof, is important as well as spreading or distribution property, i.e. the ability of the pad to transport exudate in directions parallel to the plane of the upper surface of the wound bed. Finally, the wound pad shall also provide a moist environment above the wound bed for promoting wound healing.
Thermoplastic and thermo-set open-celled foams as well as cellulose-based materials are often used as absorbent articles, such as wound pads or parts thereof. Foams typically have very good liquid wicking properties, i.e. ability to transport exudate away from the wound bed in directions perpendicular to the plane thereof, but relatively poor spreading properties. These poor spreading properties are associated with the risk that such a foam, when used as a wound pad, will be locally saturated and leak long before the theoretical absorption capacity of the foam is reached, which results in exudate getting back down to the wound bed and causing damage to the surrounding skin, a phenomenon often referred to as maceration. It is known, see for example WO 2005/021622, to improve the spreading properties of foams by partly or wholly compress foams using heat and pressure to re-orientate a majority of the cells to ellipsoidal cell shape. Such a compression will lead to improved retention properties but impaired absorption capacity as well as liquid acquisition properties due to the decrease in cell sizes.
Compression also leads to a stiffening of the foam so that a too high degree of compression will negatively influence the conformability of a wound pad, i.e. the ability of the wound pad to conform to the contour of the part of the body of a patient to which a wound dressing containing such a wound pad is applied.
It is for both practical and aesthetic reasons desirable that wound pads are thin. However, a thin body of uncompressed foam material tends to have too poor absorption and retention properties to be used as a wound pad or as a layer in a wound pad.
It is an objective of the present invention to provide a wound pad comprising a body of compressed open-celled foam of thermoplastic or thermo-set material, which has good conformability, spreading, retention and liquid acquisition properties and adequate absorption capacity as well as a method for manufacturing such a wound pad enabling a variation of the combined spreading, retention and liquid acquisition properties of the body without sacrifice of conformability.